Because explosive materials are inherently dangerous, there is extensive government regulation concerning their manufacture, use, and transportation. That danger necessarily makes the business of explosives expensive as well. Consequently, explosive materials which are relatively safe to handle, but which must be primed or sensitized immediately prior to detonation are highly desirable.
Nitromethane, for example, is an extremely powerful explosive, yet it is very stable. Unfortunately, it is so stable that its reliable detonation has been a problem which even today is not remedied completely.
It is well known that nitromethane can be sensitized by incorporating, usually with gelled nitromethane, sensitizing compounds, e.g., nitromethane soluble amines, or sensitizing materials, e.g., microspheres or microballoons. Microspheres are frangible articles and generally are very small, spherically shaped, and made of glass or glass-like substance. Microballoons are microspheres which have a hollow, gas-containing cavity.
Unfortunately, conventional nitromethane gels usually cannot be made at the site of their intended use, and they must be transported and handled in their sensitized condition. Safety concerns are increased correspondingly. Thus, DET devices have been developed which can enhance the detonating effect of conventional blasting caps to enable them to detonate nitromethane.
For example, U.S. Pat. No. 3,794,534 to O. Chandler (Chandler) discloses a DET device which comprises an open-celled polymeric foam having microballoons dispersed within and embedded on the surface of the foam. A preferred method of making the DET device comprises mixing the microspheres in a foam monomer and then foaming the monomer. Another preferred method comprises shaking or tumbling relatively thin pieces or shreds of a foam in microspheres to embed or enmesh the microspheres in the foam at its surface.
U.S. Pat. No. 3,797,392 to R. Eckels (Eckels) also discloses a DET device. The Eckels DET device is formed from, inter alia, a porous body and microspheres. The microspheres are spatially located in a relatively inhomogeneous fashion and are intimately dispersed in the porous material. A preferred method of making such DET devices comprises mixing microspheres in a urethane foam resin and then curing the resin into a foam.
Unfortunately, the DET devices disclosed in Chandler and Eckels require relatively strong blasting caps for detonation of liquid nitroparaffins. For example, the Chandler device in combination with a No. 10 blasting cap successfully detonates nitromethane. Chandler discloses, however, that if the microspheres are secured to the foam surface by an adhesive, as opposed to dispersing and embedding them in the foam surface, the DET device did not enable even a No. 16 blasting cap to detonate nitromethane. The microsphere-dispersed-foam DET devices of Eckels appear to offer some improvement, it being disclosed therein that No. 6 blasting caps are capable of detonating nitromethane when combined with the Eckels DET devices.
Prior to the present invention, it was not thought possible to detonate liquid nitromethane with relatively low power blasting caps, such as a No. 3 cap. Because their relatively low power makes them safer to handle, however, No. 3 blasting caps are preferred over Nos. 6, 8, 10 or 16 blasting caps. Also, because they are less expensive than higher-numbered blasting caps, No. 3 caps are preferred for cost reasons.
Thus, it is a general object of this invention to provide a DET device which permits the detonation of a body of liquid nitromethane through the use of a safer, less expensive, relatively low-power blasting cap.
Another object is to provide a method of explosively detonating liquid nitromethane, through the use of an improved DET device in combination with a relatively low-power blasting cap, e.g., a No. 3 blasting cap.
These and other objects and advantages of the invention will be apparent to those skilled in the art upon reading the following detailed description and upon reference to the drawings.